Fluorescent lighting has long been commonplace especially in commercial, institutional and industrial applications. The energy efficiency of fluorescent fixtures coupled with relatively low fixture costs cause fluorescent lighting to be the lighting of choice in most office situations as well as in numerous other task lighting applications. In commercial applications, overhead lighting systems are commonly found in buildings that utilize “dropped” or suspended ceiling grid arrangements, which are normally hung from the floor platforms of the story located immediately above. Typical overhead lighting systems comprise a light fixture housing, or troffer that is conventionally designed in the shape of shallow, inverted, rectangular box having one open face. A series of light fixture housings or troffers are usually installed in the dropped ceiling grid, with each troffer carrying at least one light source, such as a tubular lamp, therein.
Oftentimes, a transparent or translucent lens may be used to cover the open face of the light fixture housing. Such lenses can be undesirable if they are not particularly designed to effectively prevent the escape of low angle light rays from the light fixture housings. These low angle light rays may create a glare that can be irritating to those individuals located in the space that the overhead lighting systems are designed to illuminate.
Accordingly, the use of either coffers or louvers has been proposed in the past for eliminating or minimizing glare. Conventional coffers are rectangular recesses formed in a ceiling at spaced intervals that are designed to house the light fixture housings. In order for a coffer to effectively reduce glare, it must have deeper dimensions than the light fixture housings that it will contain because the light fixture housings are usually installed in the upper surface or wall of the coffer, which allows the remaining side walls of the coffer to act as barriers to escaping low angle light rays. Though generally effective in reducing glare, coffers are often costly to install, and in certain instances, coffers may be impossible to install if the architectural design of the building prevents it.
Louvers help to reduce glare by directing the light radiating from the troffer generally downwardly. A typical louver comprises a grid-like structure that includes a series of V-shaped or parabolic shaped blades (or baffles) arranged perpendicular to one another and interlocked to form a series of more or less equally sized square or rectangular openings. Generally, louvers are mounted directly beneath the lighting tubes of light fixture housings, or troffers, such that the bottom edge of the louver is more or less flush with the plane of the ceiling.
A louver is typically assembled from a series of lateral and longitudinal metal blades. It has also been known to fabricate single-piece, plastic louvers using conventional injection molding techniques. Plastic louvers may be undesirable, however, because of deterioration that can result due to the louver blades proximity to light sources that generate substantial amounts of heat. Whether metal or plastic, the blades of most louvers are typically designed with parabolic side wall surfaces that are shaped to reflect the light emitted from the lamps downward in an effort to minimize the escape of the low angle light rays that produces glare. Typically, in order to create the parabolic shape for the blade side wall, the top edge surface of the blade is wider than the lower edge surface. This wide area along the blade upper edge surface acts to block a portion of the light emitted from the light source, i.e., lamp, and reflects it back into the light fixture, which negatively impacts the light fixture efficiency.
Louvered troffers generally set the standard in architectural lighting for most commercial and institutional applications and have become essential components of the very architecture of high activity environments. Thus, it is desirable to provide louvered fixtures which can be manufactured at minimum cost yet exhibit exceptionally high performance and provide a visually aesthetic appearance in their operating environment. Further, these low-cost, high performance louvered fixtures must be rapidly installable and must yield ever-increasing energy efficiencies while producing desired illuminance levels. Contemporary lighting systems and particularly louvered troffer systems must therefore provide a marriage of aesthetics and performance at minimum manufacturing costs.